1. Field of the Invention
The invention generally relates to methods for delaying the abscission, preharvest drop, ripening, maturation, senescence or pathogen entry of produce such as fruit and vegetables. In particular, the invention provides a method of temporarily preventing or delaying the ripening or maturation of produce by the pre- or post-harvest application of a photosynthetic pigment or membrane stabilizing agent and osmoregulaor such as glycine betaine.
2. Background of the Invention
Postharvest treatment with the synthetic molecule 1-methylcyclopropene (1-MCP) is used by the fruit industry to slow the ripening process of fruit during storage. 1-MCP treatment extends the shelf life of treated fruit, thereby increasing the availability of fresh fruit to consumers throughout much of the year. 1-MCP is structurally related to the natural plant hormone ethylene and slows ripening by binding to ethylene receptors, thereby blocking the binding of ethylene and preventing a ripening response to the hormone. In some cases, over time, the effect of 1-MCP treatment wanes and ripening of the treated commodity can occur. The use of 1-MCP in this manner is described in U.S. Pat. No. 6,017,849, the complete contents of which are hereby incorporated by reference in entirety.
Unfortunately, certain fruits do not respond well to 1-MCP. For example, applications of 1-MCP have had mixed success in pear storage, often yielding pears that are unable to ripen at all after treatment. The resulting pears remain hard and have relatively low levels of soluble sugars, which impair their taste and appeal to consumers. For these and other types of fruit, there is a need in the industry to provide alternative methods for the treatment of fruit to slow the ripening process. It would also be desirable to have available an anti-ripening agent that is a natural product rather than a synthetic such as 1-MCP.
Several attempts to control or delay ripening of fruits and vegetables during transport and storage have been made. For example, U.S. Pat. Nos. 6,124,525, 6,080,914, 5,952,546 and 5,512,466 describe various genetic modifications of plants that may be used to alter the ripening process. However, the use of genetically modified organisms is generally not popular with the public at large, may have far-reaching and unpredictable environmental consequences, and requires a high degree of government regulation.
U.S. Pat. No. 7,943,549 to Pierce et al. describes methods for delaying a plant development process by exposing a plant or plant part to one or more bacteria or enzymes. Bacteria such as Rhodococcus spp., Pseudomonas chloroaphis, and Brevibacterium ketoglutamicum may be used. However, the use of live organisms can be fraught with problems since they are sensitive to environmental conditions, and control of the process (e.g. reversibility) may be difficult. In addition, the public may be reluctant to consume produce that has been “infected” with bacteria.
Glycine betaine is known to be used as an osmolyte regulator when applied to fruit before harvesting so as to prevent or reduce blemishes or damage of the skin of the fruit (e.g. to reduce cherry cracking; see U.S. Pat. No. 5,972,840 to Mottram, the complete contents of which are hereby incorporated by reference). However, U.S. Pat. No. 5,972,840 makes no mention of the use of glycine betaine to forestall ripening or prevent pathogen entry of fruit or other produce.
In addition to its role in ripening, ethylene plays a role in abscission, the process of a plant intentionally shedding an organ. Plants naturally use the process of abscission to drop fruit at the end of a growing season. While this process is beneficial in nature, dropping fruit before harvest leads to large losses in the agricultural world. U.S. Pat. Nos. 5,869,424 and 6,153,559 addresses this issue through the application of aminoethoxyvinylglycine (commercially named RETAIN®) and its precursor N-acetyl aminoethoxyvinylglycine, respectively, to inhibit ethylene biosynthesis. An alternative strategy was described in U.S. patent US 2012/0101164 A1 where application of 1-naphthaleneacetic acid (NAA) also delayed the abscission of fruit. However, these approaches act through different mechanistic properties compared to glycine betaine.